Vacuum dehydration of carrots



Patented June 25, 1946 VACUUM DEHYDRATION OF CARROTS Robert M. Schaffner, Chicago, Ill., assignor to The Guardite Corporation, a corporation of Illinois No Drawing. Application June 28, 1944,

Serial No. 542,601

2 Claims. (C1. 99-204) v This invention relates to the vacuum dehydration of carrots.

The carrots are first peeled by abrasion or chemical methods and are then washed and sliced or diced into small pieces. It is preferred that the thickness be not over inch or less than V; inch. The diced or sliced carrots are then loaded on screen bottomed drying trays at loading densities of 1.0 to 1.5 lbs. per square foot and preferably at 1.3 lbs. per square foot. Sliced carrots in which the slice is wider than its thickness are preferably loaded at the lower densities, and

'cu'bical particles may be loaded at the higher densities.

The trays are then placed in a vacuum blancher and the pressure reduced to remove the air. This may suitably be accomplished by reducing the pressure to about /2 inch of mercury andthen admitting saturated steam to raise the pressure and temperature to that suitable for blanching. This is preferably between 190 and 220 F. corresponding to a pressure between 19 inches absolute of mercury and 2 lbs. per square inch gauge. The temperature is maintained for a sufllcient time to secure proper blanching. At 201 F., 10 minutes is suitable. However, a time of 10 minutes was also suitable at 193 F., and a time of 15 min utes at 204 F. has been used without damaging the carrots.

After completion of the blanching operation, it is preferred to cool the-carrots by reducing the pressure in the chamber to about inch absolute, this reduction bringing the carrots to a temperature in the neighborhood of 59-450 F.

The carrots are then transferred to a vacuum drying chamber without contact with the atmosphere. A suitable drying chamber for carrying out the process is shown in Heineman application 520,773, filed February 2, 1944, and Beer applica- @1011 filed February 28, 1944. This system comprises an elongated rectangular drying chamber having means at one endfor admission ofthe products to be dried and at the other for removing them, in each case, without admitting air to the chamber. The products are carried through the system on trays arranged in 6 vertical tiers. coils above and below the trays. These coils are arranged in 9 consecutive banks and may be heated to diiferent temperatures. Each coil has an exterior diameter of approximately 2% inches with V inch between the pipes or coils. The bottoms of the trays are approximately 3 inches from the nearest point on the coils above and below them. The system is operated under ,a pressure of approximately 2 inches mercury absolute, the atmosphere being superheated steam. Superheatedsteam is admitted to the system near the entrance and near the exit and is withdrawn from the central portion of the device.

It will be observed that the carrots, when introduced to the system are cool, and have been under a lower pressure so that there is some tendency for a small amount of moisture to condense on the surface of the carrots Just as they are introduced to the drying system, and-are subjected to intense radiant energy for the first time. It has been found that the radiant heat surfaces may be maintained, for the distances described, as higher as 330 F. Finishing temperatures as low as 200 F. have been employed successfully.

A satisfactory drying cycle was obtained under the following conditions with tray loading densities of 1.3 lbs. per square foot:

The following table gives operating data on a Each tray is. surrounded by heating.

The dehydration ratio is the raw weight divided by the dehydrated weight. The rehydrae tion ratio is the rehydrated weight, dividedby the dehydrated weight. The rehydrated weight is taken after heating the dehydrated carrots in boiling water for 30 minutes without any previous soaking. The reconstitution percentage is the rehydration ratio divided by the dehydration ratio.

The foregoing detailed description has been therefrom.

What I claim a new and desire to secure y Letters Patent is:

1.-The method of drying carrots which com- 1 prises cleaning the carrots loading on screens at source maintained at between 200:to 330 F. and

located approximately 3 inches from the carrots. 2. The method as set forth in claim 1, in which at the conclusion of the blanching operation the pressure is reduced to cool the carrots and produce a pressure below the operating pressure in the vacuum drying system.

aosaa'r M. SCHAFFNER.

number of operations on r d cored hant nay densities or 1.0"to 1.5 lbs. per square toot, removing carrots: substantially all air therefrom, replacing the air.

. [Operating vacuum pressure 57 mm.] I

" 1 r a 2 a 4 s a 7 I l 1 VARiETY-RED CORED CHANIENAY Processing:

Hrs. after harvest 27 72. 24. Orig. moisture ..percent. 88.5 87.7 88.8 89.0. Final moisture do 3.9 4.0.; 18.5 2.1. Color of rehyd. prod. Excellent Excellent ExoellenL. Some burned. Flavor of rehyd. prod .do Good. Texture of rehyd. prod D0. Dehydration ratio 10.8. Rehydration ratio (30 min. boll-no soak) 6.50. Reconst percent. 60.9. .Pretrpatment-t'vashed, peeled, dice for all:

Loading ibs./sq. it. 1.34. Machine blanch Min 10- 10 l l0 i 10. Temp 193 211 1.. 199 196 F 204 F- 106 F 200 F. Drying cycle: P M P M P M P M P M P M P M Pp. s. i. stem. 60 30 30 70 30 70 30 00 36 32 M-minutes. 20 0 N 30' 20 30 20 30 20 30 20 36 60 18 

